1. Field of the Invention
This invention relates to a cartridge for firearms, comprising a plastic case which contains a propellant charge and a priming material, and which at its head end constitutes a bushing-like socket containing a projectile.
2. Description of the Prior Art
Cartridge cases do not serve only to interconnect the projectile, propellant charge and primer and to protect said parts but, above all, are intended to ensure a firm and centering retention of the projectile and to contribute to the sealing of the chamber of the firearm as the propellant charge is ignited and the round is discharged. To meet said requirements, the cases of most live cartridges have previously consisted of metal although this involves high manufacturing costs and a heavy weight of the cartridge. Attempts to use caseless cartridges have not been successful because without the protecting, guiding and sealing actions of the case the effect of the cartridge is not ensured and the firearm becomes unreliable.
Plastic cartridge cases have been provided in an effort to retain the advantages afforded by a cartridge case but to reduce the manufacturing costs and the cartridge weight. Such plastic cartridge cases have a sufficiently strong bushing-like socket, in which the projectile is sufficiently safely and sealingly retained whereas the propellant charge is contained in the interior of the case adjacent to the socket. The priming material consisting, e.g., of a primer cap is centrally disposed in the case adjacent to its bottom so that an axial firing pin or other axially acting firing means are required. But such firing means are rather expensive and liable to be deranged and add to the overall length of the firearm. Besides, said firing means and the centrally disposed primer caps or the like associated with them permit a point-ignition of the propellant charge so that the propellant charge is not completely burnt and, as a result, propelling force may be reduced and residues of unburnt powder may be left. Besides, plastic cases which owing to their low strength remain in the chamber after the round has been discharged cannot simply be extracted, like metal cases, from the chamber by extractor hooks. For this reason, cartridges having plastic cases cannot reliably be discharged unless special breechblock and loading means are used which are provided with a loading member that constitutes the chamber and is separate from and transversely movable relative to the barrel. For this reason that loading member can be moved from a firing position, in which the chamber is coaxial to the barrel, to a loading and unloading position, in which the chamber is open and, above all, the plastic cases can satisfactorily be ejected from the chamber. But in that case the plastic case must perform important sealing functions in the chamber for the discharge of the round and that object is often only poorly accomplished in cartridges which have bottom primers and are associated with corresponding firing means. Besides, the bottom of the plastic case must have a substantial wall thickness for a reliable accommodation of the primer cap or the like so that the case volume that is available for the propellant charge will be reduced or the length of the case will be increased.